<!DOCTYPE html>
<html>

<head>
    <title>Planet Information</title>
    <style>
        body {
            font-family: Arial, Helvetica, sans-serif;
            background-color: #121212;
            color: #ffffff;
        }

        h1 {
            text-align: center;
            margin-top: 50px;
        }

        form {
            text-align: center;
            margin-top: 30px;
        }

        label {
            font-weight: bold;
            display: block;
            margin-bottom: 5px;
        }

        input[type="text"] {
            padding: 8px;
            border-radius: 4px;
            border: 1px solid #ffffff;
            width: 200px;
            background-color: #292929;
            color: #ffffff;
        }

        input[type="submit"] {
            padding: 8px 20px;
            border-radius: 4px;
            background-color: #4CAF50;
            color: #ffffff;
            border: none;
            cursor: pointer;
        }

        input[type="submit"]:hover {
            background-color: #45a049;
        }
    </style>
</head>

<body>
    <h1>Planet Information</h1>
    <form action="/" method="POST">
        <label for="planet">Enter a planet name: (e.g. Mars)</label>
        <input type="text" id="planet" name="planet">
        <br><br>
        <input type="submit" value="Submit">
    </form>
</body>

</html>